THE SIGNIFICANCE OF CHROMOSOMAL TRANSLOCATION INVOLVING BCL6 GENE IN MALIGNANT LYMPHOMA

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We identified two regions in the BCL6 gene that negatively regulate BCL6 expression. One region, ES, is located within the first and a second region, IS, is located within the first intron. A consensus nucleotide sequence for the binding of the BCL6 protein itself was found within the ES. The IS region which is included in the regions commonly deleted in B-cell lymphomas had a silencer activity. Structural alterations of these two regions may play roles in the deregulated expression of the BCL6 gene in B-cell lymphomas.We report a case of non-Hodgkin's lymphoma of unknown origin with invasion into bone marrow and brain. Using FISH and SKY technique, we identified the new partner site of the 14q32 translocation, 22q13, and the jumping translocations involving 2p23 as a new donor chromosome. We could also identify the unbalanced translocation of t(3 ; 14)(q27 ; q32). The combination of SKY and FISH using the 14q telomere probe was therefore considered very useful for the characterization of complex cytogenetic cases in B-cell lymphoma.We cloned the human BAZF gene, homologue of protooncogene BCL6, using murine BAZF as a probe. The predicted amino acid sequence was 91% identical to that of murine BAZF. Fluorescence in situ hybridization analysis revealed that the human BAZF gene is located on chromosome 17p13.1. Although expression of human BAZF mRNA was ubiquitously detected in human tissues, abundant expression was detected in heart and placenta. BAZF mRNA was expressed in some immature B cell lines and erythroleukemia cell lines. The expression in a human erythroleukemia cell line, HEL cells, was upregulated during megakaryocytic differentiation induced by TPA.